1. Field of the Invention
The present invention relates to a substrate for growing carbon nanotubes, a manufacturing method thereof, and a manufacturing method of oriented carbon nanotubes.
2. Background Art
Hitherto, there has been known an oriented carbon nanotube manufacturing method by the usage of a plasma CVD for manufacturing oriented carbon nanotubes oriented in a perpendicular direction to a substrate in the synthesis of multi-walled carbon nanotubes for an electric field emitter (for example, refer to Science, 282, 1105 (1998)).
According to the method by the usage of plasma CVD, the improved field effect by a sheath formed by the plasma has been considered to contribute to the orientation of carbon nanotubes. However, there is such a problem in the method by the usage of plasma CVD that while carbon radicals are being generated in a plasma generation area, the substrate is attacked by ions generated as a by-product of the carbon radicals, which caused the growing carbon tubes to be etched.
Thereby, the method by the usage of plasma CVD is disadvantageous in growing long carbon nanotubes, and it is more disadvantageous in growing single-walled carbon nanotubes since the single-walled carbon nanotubes are subjected to etching easier than the multi-walled nanotubes.
In order to solve the mentioned problem, the inventors disclosed an art where the substrate is held at a distance to the plasma generation area which is capable of preventing the substrate from being attacked by the ions generated as a by-product of the radicals generated at the plasma generation area and is reachable by the radicals at a radical state in an antenna-type plasma CVD (refer to Japanese patent Laid-open No. 2006-36593).
In the mentioned art, the substrate is provided with a reaction prevention layer which is formed on a base material which prevents reaction between the base material and a catalyst material, a catalyst material layer which is formed on the reaction prevention layer, and the catalyst material layer is further formed with a dispersion layer which disperses the catalyst material contained in the catalyst material layer.
According to the mentioned configuration, it is possible to prevent the substrate from being attacked by the ions originated from the plasma; since the substrate is unnecessary to be exposed to a high temperature, it is also possible to inhibit thermal aggregation of catalyst. Consequently, it is possible to manufacture oriented carbon nanotubes formed from long single-walled carbon nanotubes.
However, when the conventional substrate is used, elongation of the single-walled carbon nanotubes of an average diameter of equal to or larger than 2 nm may be achieved, but there is a drawback that the single-walled carbon nanotubes of the average diameter of less than 2 nm may not be elongated to a length of equal to or more than 400 μm.